The clarity of recreational waters is an important measure of overall water quality. Water can become cloudy as bacteria (dead and alive) and swimmer wastes accumulate, overwhelming the system's filtering capacity. Oxidizers such as chlorine, bromine, hydrogen peroxide and potassium peroxymonopersulfate are routinely used to achieve and maintain clear water. However, there are drawbacks to using oxidizers to fulfill this function. For example, chlorine and bromine levels must be maintained at levels of 1-3 ppm (as Cl.sub.2) and periodic superchlorination may be required to assure microbiological control and adequate water quality. Hydrogen peroxide and potassium peroxymonopersulfate must be used in much higher concentrations because they are weaker oxidizers than chlorine and bromine.
In spite of the drawbacks identified above, chlorine is still the most widely used water sanitizer because of its effectiveness and relatively low cost. In recreational waters, chlorine provides clean, clear water as long as its levels are appropriately maintained. However, as chlorine has come under sustained environmental scrutiny, the need for efficacious, low or non-chlorine alternatives has arisen. Moreover, recreational customers often complain of skin and eye irritation as well as discolored swimming wear after swimming in halogenated water.
As a result, the use of non-halogenated sanitizers and oxidizers has increased throughout the water treatment industry. For example, polyhexamethylene biguanide (PHMB) and hydrogen peroxide have gained increasing acceptance in the pool and spa industry for sanitation and oxidation, respectively. Consumers have indicated that PHMB-treated water is less irritating than chlorinated waters and will not bleach swim wear or pool surfaces.
However, pools treated with PHMB can develop problems with recalcitrant biofilms such as pink slime, mustard algae and white water mold. When problems such as these are encountered, treatment options are limited since PHMB is incompatible with traditional oxidizers such as chlorine, bromine and potassium peroxymonopersulfate. Hence, it is not uncommon for PHMB users to spend considerable amounts of time and money to remove and kill resistant microbial growths. By contrast, when similar problems arise in pools treated with halogen sanitizers, they can usually be remedied quickly and inexpensively.
Methods for combining polyquats with hydrogen peroxide and for their use as water treatment clarifiers and sanitizers have also been described. As such, polyquats have proven to be very effective stabilizers and performance enhancers for peroxide water treatment systems. Adding products such as non-polymerized surface active agents (e.g., alkyldimethyl-benzylammonium chloride and didecyldimethyl-ammonium chloride) may boost the performance of the system, but may not be readily miscible with the polyquats. In such cases, hydrogen peroxide could be used as the formulating agent to blend the immiscible compounds.
In spite of the above known combinations, commercially viable methods of utilizing combinations of halogen and non-halogen sanitizers have not been developed. The present invention addresses that need.